As the application of the Ethernet constantly expands from the local area network to the metropolitan area network and the backbone network, the Ethernet technology also evolves continuously. Institute of Electrical and Electronics Engineers (IEEE), an international organization for standardization, published an 802.1ah Provider Backbone Bridges (PBB) standard and an 802.1aq Shortest Path Bridging (SPB) standard respectively in August, 2008 and June, 2012. The two standards respectively stipulate a data plane and a control plane of the Ethernet which are applied to a network backbone layer.
A PBB data plane adopts PBB encapsulation (also referred to as MAC-in-MAC encapsulation), and the specific encapsulation format is as shown in FIG. 1, wherein Ethernet frames sent by a client (i.e. client frames) are encapsulated therein. The encapsulated client frames carry a Customer MAC Address (C-MAC) and a client frame VLAN tag, wherein the client frame VLAN tag includes 12-bit client frame VLAN Identifiers (VID). When the client frames enter the network, a layer of a new MAC address and a VLAN tag is encapsulated outside the client frames, i.e., a Backbone MAC Address (B-MAC) and a Backbone VLAN tag (B-TAG), wherein the B-MAC includes a 6-byte destination B-MAC and a 6-byte source B-MAC respectively, and the B-TAG includes a 12-bit Backbone VLAN Identifier (B-VID). The PBB standard also stipulates, aside from the B-MAC and the B-TAG, a 6-byte Backbone Service Instance tag (I-TAG) must be encapsulated between the B-TAG and the C-MAC when the PBB encapsulation is performed. The I-TAG includes a 24-bit Backbone Service Instance Identifier (I-SID). The PBB encapsulation is completed at an edge node of the network. After the encapsulation is completed, all nodes including the edge node in the network forward the Ethernet frames according to the destination B-MAC and B-VID, and the I-SID is only taken as the isolation of different service instances at the edge node of the network and does not influence the forwarding of the Ethernet frames. As regards the edge node of the network, one or more client frame VIDs at an ingress port are mapped to one I-SID, one or more I-SIDs are mapped to one B-VID and one or more destination C-MACs are mapped to one destination B-MAC.
An SPB control plane adopts an ISIS-SPB (i.e., an IS-IS applied to an SPB network) link state routing protocol. The protocol performs the corresponding customization and expansion against the Ethernet data plane, on the basis of an Intermediate System to Intermediate System (IS-IS) link state routing protocol stipulated by international standard ISO 10589. As with the IS-IS protocol, the ISIS-SPB protocol likewise includes three protocol messages, which are respectively a Hello message, a Link State PDU (LSP) message and a Sequence Number PDU (SNP) message, wherein the Hello message exchanges between adjacent nodes in the network and is used for the establishment of an adjacency between adjacent network nodes; the LSP message is flooded by any node in the network to all the other nodes; each network node uses link state information of all nodes carried by the LSP message received from all the other nodes to construct a Link State Database (LSDB) of the present node, and then an Ethernet frame forwarding table in the data plane is established according to the LSDB; and the SNP message exchanges between adjacent nodes in the network and is used for the update and synchronization of the LSDB on each network node. As with the IS-IS protocol, each ISIS-SPB protocol message may include multiple protocol message TLVs (Type/Length/Value), and each protocol message TLV may further include multiple protocol message sub-TLVs.
The SPB standard IEEE 802.1aq stipulates a sub-TLV carried by the Hello message, which is named as an SPB Base VLAN-Identifiers sub-TLV, and the specific encapsulation format is as shown in FIG. 2. The sub-TLV includes ECT-VID tuples of which the number is changeable; each ECT-VID tuple includes a 4-byte Equal Cost Tree (ECT) algorithm used for an equal cost path tie-break and a 12-bit Base Virtual Local Area Network identifier (Base VID) used for selecting the ECT algorithm, and a U flag (Use-Flag) for identifying whether the ECT-VID tuple is used by the present node and an M flag (M-Bit) for identifying an SPB working mode (including an SPBM mode using the PBB data plane and an SPBV mode not using the PBB data plane). Since each Base VID can only correspond to one ECT algorithm, the values of the Base VID in various ECT-VID tuples should be different. The SPB standard stipulates that the above-mentioned ECT-VID tuples can also be carried in an SPB Instance sub-TLV in the LSP message aside from being carried in the Hello message, and the values of each pair of ECT algorithm and Base VID that is configured by each node in the network must be completely consistent among all the nodes, otherwise, the adjacency of adjacent nodes and the LSDB of each node cannot be established so that the Ethernet frame forwarding table in the data plane cannot be established.
In order to establish the Ethernet frame forwarding table with the destination B-MAC and B-VID as the input parameters and the egress port as the output parameter in each node. The SPB standard also stipulates a sub-TLV carried by the LSP message, which is named as an SPBM Service Identifier and Unicast Address sub-TLV, and the specific encapsulation format is as shown in FIG. 3. The sub-TLV includes a 6-byte the present node B-MAC, a 4-bit reserved field, a 12-bit Base VID and I-SID tuples of which the number is changeable, wherein each I-SID tuple includes a 24-bit I-SID, a T flag for identifying whether a service flow corresponding to the I-SID is sent by the present node and an R flag for identifying whether the service flow corresponding to the I-SID is received by the present node. The above-mentioned sub-TLV can only be carried in the LSP message flooded outwards by the network edge node, and can appear many times in the same LSP message, but the B-MAC included in the appearing sub-TLV should be different each time. The SPB standard stipulates that the 12-bit Base VIDs carried in the above-mentioned sub-TLV also correspond to the B-VIDs used for differentiating different B-VLANs on a one-to-one basis, aside from being used for selecting different ECT algorithms. All the network nodes receiving the above-mentioned sub-TLV extract the B-MAC and Base VID carried therein, which are respectively regarded as input parameters, destination B-MAC and B-VID, of the established forwarding table, and then network topology information is acquired according to the LSDB, and a shortest path first algorithm and an equal cost path tie-break ECT algorithm are used to calculate the egress port of an output parameter. The SPB standard also stipulates that a many-to-one mapping relationship between the client frame VIDs and the I-SID and a many-to-one mapping relationship between the I-SIDs and the Base VID must be configured at the network edge node working in the SPBM mode, which are at various ingress ports, and a mapping relationship between the C-MAC and the B-MAC must be learnt from the PBB Ethernet frames received from other edge nodes. The above-mentioned various mapping relationships are all used for completing PBB encapsulation and decapsulation at the network edge node.
The IEEE 802.1AX-2008 standard defines the single node Link Aggregation technology that is to logically bind multiple physical links which connect one node and its the same one adjacent node so as to be used as one logical link, i.e., a Link Aggregation Group (LAG), achieving the load sharing of the service flow among these multiple physical member links constituting the LAG Under the condition where some of the member links have a fault, the service flow is fast switched to other fault-free member links, thereby achieving the redundancy protection function. Currently, the IEEE 802.1AX-REV project is revising and expanding the single node link aggregation technology defined by the 802.1AX-2008 standard, and aims to formulate an inter-node link aggregation working mechanism that can logically bind multiple physical links which connect one or more (two or three) nodes and multiple (two or three) different adjacent nodes so as to be used as one logical link. The purpose thereof is consistent with the single node link aggregation technology about achieving the load sharing and redundancy protection of the service flow among the LAG member links. The 802.1AX-REV draft standard (version D0.4 published in October, 2012) stipulates that, when achieving the inter-node link aggregation technology, as shown in FIG. 4, one or more nodes at a side of an inter-node LAG constitute a portal together, each node constituting the portal has an unique Portal System Number, and the value range of the number is an integer from 1 to 3. If multiple nodes constitute one portal, there must be a physical link named as Intra-Portal Link (IPL) among the multiple nodes, which is regarded as a channel of exchanging information required by multiple nodes in a portal for completing the link aggregation.
In order to solve the problem encountered when a single customer device uses the inter-node link aggregation technology to access a Provider Link State Bridging (PLSB) network via multiple network edge nodes, which is also named as accessing in a multi-homing manner, an issued U.S. Pat. No. 8,270,290 (Resilient Attachment to Provider Link State Bridging (PLSB) Networks) proposes a solution. The PLSB network mentioned in the patent is the predecessor (another appellation) of the SPBM network stipulated by the above-mentioned standardized 802.1aq, and adopts a PBB data plane and an IS-IS control plane. The patent mainly solves two problems. As shown in FIG. 5, the first problem is described as follows. Client flows from a customer device respectively enter into an edge node 1 and an edge node 2 via load sharing, and the edge node 1 and the edge node 2 perform the PBB encapsulation respectively on the client flows entering the PLSB network. The flows after the encapsulation from the edge node 1 and the edge node 2 may be received alternately at a far-end edge node (e.g. an edge node 4). If the edge node 1 and the edge node 2 adopt different B-MACs to perform the PBB encapsulation, when a mapping relationship between the B-MAC and the C-MAC is learnt at the far-end edge node according to the received flows, repetitive flip-flop of mapping the same C-MAC to different B-MACs may appear, and this needs to be avoided. As regards the first problem, the patent proposes the solution that customer ports which are distributed on different edge nodes and belong to the same LAG are configured with the same B-MAC, and meanwhile, a pseudo node is simulated on an IPL connected to different edge nodes; a real edge node represents the pseudo node to flood the LSP message carrying pseudo node link state information to other nodes in the PLSB network, and the real edge node pretends to be a neighbour node of the pseudo node so as to flood outwards the LSP message carrying the link state information of the present node; and other nodes in the network establish the LSDB via multiple received LSP messages and calculate the Ethernet frame forwarding table directing to the pseudo node. The second problem is described as follows: the flows from the far-end edge node (e.g. the edge node 4) to the customer device may be sent either to the edge node 1 or to the edge node 2, which can only passively select a forwarding path with a low cost according to the shortest path first algorithm adopted by the IS-IS protocol, and lacks an active and controllable method for selecting a destination node between the edge node 1 and the edge node 2. As regards the second problem, the patent proposes the solution that the customer ports which are distributed on different edge nodes and belong to the same LAG are configured with respectively different B-VIDs, and each edge node floods out the same B-MAC and the respectively different B-VIDs together. In this way, Ethernet frame forwarding table entries going towards the edge node 1 and the edge node 2 are respectively established on the other nodes in the network according to different B-VIDs.
Aiming for the above-mentioned two problems, although the issued US patent U.S. Pat. No. 8,270,290 proposes the corresponding solutions, the two solutions both have defects. The defects of the solution of the first problem mainly lie in: firstly, it is complicated to be implemented, because the method requires the real edge node to simulate the pseudo node to flood the LSP message outwards; secondly, the introduction of the pseudo node LSP will increase the flow burden of the LSP messages in the network and the burden of each node to process the LSP messages, especially for a network which has a lot of customer devices which accesses via the inter-node link aggregation technology. The defects of the solution of the second problem mainly lie in: firstly, the manual configuration is more cumbersome and is error-prone, because the solution requires each edge node located in the same inter-node LAG to be configured with a completely different B-VID; secondly, it has poor compatibility with the published SPB standard IEEE 802.1aq, because the SPB standard stipulates that the Base VID notified by each edge node flooding outwards can be used to select the ECT algorithm and can also be used to present the B-VID, and requires the Base VIDs notified outwards by all the nodes in the network are completely consistent, but the solution requires each edge node located in the same inter-node LAG to notify outwards the completely different B-VID respectively.
No effective solution has been presented for the above-mentioned defects.